This invention relates to generally analyzing gaseous and solid materials, and in particular to components containing oxygen, and more particularly to an oxygen analyzer capable of quantifying microgram quantities of oxygen.
Numerous methods and apparatus have been developed for the analysis of matter, particularly by different types of pyrolysis ovens utilizing various types of sample holding structures and product evaluation techniques. These prior know approaches are exemplified by U.S. Pat. Nos. 1,515,237 issued Nov. 11, 1924 to T. D. Yensen; 3,252,759 issued May 24, 1966 to W. Simon; 3,374,065 issued Mar. 19, 1968 to O. L. Kolsto; 3,861,874 issued Jan. 21, 1975 to A. E. Krc; 4,244,917 issued Jan. 13, 1981 to R. A. Woods et al; 4,800,747 to T. S. Uji et al; 4,744,805 to Maroulis et al; and 4,741,817 to Croset et al.
There are currently two known and established procedures, either of which may be used in analyzing devices. The most common of these two processes involves a system in which a weighted sample is placed in a quartz pyrolysis tube containing platinized carbon. Oxygen in the gaseous combustion products are converted to carbon monoxide by passage through the platinized carbon and the carbon monoxide is subsequently oxidized to carbon dioxide by passage over copper oxide. The sample is pyrolyzed in a helium atmosphere so that carbon monoxide is formed from oxygen in the sample and so that the platinized carbon does not burn. The carbon monoxide is oxidized by the copper oxide to form carbon dioxide, which is detected and measured, giving the total oxygen concentration in the sample. This procedure or process may, for example, be carried out in a Perkin-Elmer Model 240 Elemental Analyzer made by Perkin-Elmer Corp., Norwalk, Connecticut, which incorporates features of above-referenced U.S. Pat. No. 3,252,759.
The other of these procedures or processes uses the normal inert gas-fusion method as a basis for determining oxygen released at successively higher temperatures. The sample is heated in a graphite crucible, current is increased in discrete steps using a program tailored for the specific oxides believed to be present. The oxygen peaks are plotted against temperature on an integral printer, yielding information about individual compounds present in the sample. This process may, for example, be carried out in a LECO RO-16 Oxygen Determinator, made by LECO Corp., St. Joseph, Mich.
While the above-referenced processes and apparatus have been effective, they have been found to lack the necessary sensitivity for certain types of analysis. Thus, a need exists for an oxygen analysis procedure and apparatus which provides greater sensitivity than the currently know approaches.
U.S. Pat. No. 4,601,882 discloses an oxygen analyzer which identifies and classifies microgram quantities of oxygen and ambient particulate matter and for quantitating organic oxygen in solvent extracts of ambient particulate matter. A sample is pyrolyzed in oxygen free nitrogen gas and the resulting oxygen quantitatively converted to carbon monoxide by contact with hot granular carbon. Two analysis modes are made possible; 1) rapid determination of total pyrolyzable oxygen obtained by decomposing the sample at 1135.degree. C. or 2) temperature programed oxygen thermal analysis obtained by heating the sample from room temperature to 1135.degree. C. as a function of time. The analyzer basically comprises a pyrolysis tube containing a bed of granular carbon under N.sub.2, ovens used to heat the carbon and or decompose the sample in a non-dispursive infrared CO detector coupled to a minicomputer to quantitate oxygen in the decomposition products and control oven heating. However, it has been found that the resulting analyzer lacks the necessary sensitivity for certain types of analysis.